I think we need to get away from the "natural" vs "artificial" distinction. One big problem is that we literally don't have any characters (at least ones that have been accepted) that received their powers "naturally". So, let's go through them, shall we?
I personally liked how fdeviant went about his explanation of Meta and a different point to cover, it was a bit less... harsh to me. Namely, right now, you're only considering the ones who are already active. Not the ones in S2 or future.
From the list in the OP, there are three characters that probably would be considered having "natural" abilities. However, even being born with the powers can be problematic. Spider-Man, according to your guys' definition, would be a metahuman because his powers were not "natural". However, would you consider his daughter (either Mayday in MC2 or Anna in Renew Your Vows) a mutant or a metahuman (or mutate in Marvel terminology)? Mayday/Anna were born with their powers, bu they inherited their powers from their father, who did not receive his powers naturally. So would she be a mutant or a metahuman?
It depends on the abilities, are they identical to Spiderman's to the very letter? If so, I would consider they would be meta due to the fact the abilities were passed but their origins are still unnatural. If their abilities altered and weren't exact, say they lacked webbing or wallcrawling or had venom, than I would lean toward mutation since the genes might've been triggered and were there all along.
Lyger, from what NSM stated, I classed as a mutant as his abilities were originally there but triggered by the meta blood which is similar to the argument you stated. I could even argue, based on what you stated, he could be a bit of both since they combined (though a bit odd to me).
This is the main reason I've not bothered to make a scientific PC or even detail Gene Co's work because I don't want to block people into a set line of thinking, even if I enjoy the aspect and like exploring it in writing.
This line of thinking could even be taken further. So, mutants are supposed to be created by evolution. But what if the first mutants were really just humans that have been altered by either aliens (as the mainstream Marvel mutants are) or by other humans (as the Ultimate Universe mutants were). This even expands to the Inhumans, who were experiments by the Kree. Where is the line drawn? Sure, after several generations, the powers would be "natural" because nothing beyond dominant genes would cause them, but that gene was created artificially to begin with.
See, the bad part of a sandbox with such loose rules is it doesn't matter what I think or create. I can set ideas for my own creations, but someone is going to alter it or change it in some fashion because they don't like the idea .In truth, there's so many ways to look at it as comics have proven. This is the main reason I brought up the conversation at all as see what others though, and maybe share my own views. I never pushed. I even admitted to fdeviant I never looked at the Meta term in that fashion until he brought it up, proving I can shift my thoughts when it's explained in a different way. Despite how it sounds, nothing I state is set in stone even if it is placed into the IC because it won't be universal or likely everyone will accept it.
Therefore, I think that a better schema would be the source of the powers. Are they hybrids? Are the powers the result of a gene(s)? Are the powers magically induced?
Isn't that more of a break down for description? Like how scientist class animals where they have Genus, Family, etc rather than board terms and such as we were discussing about?
